Conventionally, a known power switching circuit switches the power by comparing a voltage from a first power supply and a voltage from a second power supply, as proposed in Japanese Laid-Open Patent Publication No. 2008-125176, for example.
A chattering in which the switching of the power supplies is repeated may occur when voltage values of the voltages from the power supplies remain approximately the same. However, when the voltages that are compared are obtained from the power supplies via respective resistor voltage dividers, an amount of change in each voltage-divided voltage is small compared to an amount of change in the corresponding power supply voltage. For this reason, in a case in which a detection accuracy of the voltage-divided voltages becomes inconsistent, the switching of the power supplies may not be stable.
For example, in an IC (Integrated Circuit) tag having a low power consumption and a small circuit area, the power consumption of resistors in the resistor voltage divider and the circuit area may affect communication performance and cost of the IC tag.